Multi-node model of VVER-1200 reactor dynamics for automatic control system synthesis

This paper presents multipoint kinetics of the VVER-1200 nuclear reactor model determined under the Avery coupled reactors formulation. Different numbers, from two to twenty, of axial nodes are modelled in MATLAB. For a more precise description of the transient’s nature, this model was extended by Mann’s thermal hydraulic model. Within the frame of Mann’s approach, one fuel node is adjacent to two coolant nodes. For daily maneuvering modes space-dependent xenon oscillations are considered and the Axial Xenon Oscillation Index is introduced. This paper also introduces the novel nodal mathematical model of the boron acid which is coupled with thermal hydraulic model by coolant mass flow rate. The computational results show that the accuracy of the proposed model is more than satisfactory, and general assumptions about transients align with their physical definitions. This research contributes to the advancement of the point-like nuclear reactor modeling for further improvement of the automatic power controller design.